IDENTIFICATION SYSTEM GUIDELINES
Saeid Ahmadi JazaniGRAPHIC SYMBOL SYSTEM GUIDELINES
General
This subsection establishes an identification system for instrument loop devices and functions. It is logical, unique, and consistent in application with a minimum of exceptions, special uses, and requirements. The identification system is used to identify instrumentation in text, sketches, and drawings when used with graphic symbols as described in the subsection titled “Graphic Symbol System Guidelines.”
The identification system provides methods for identifying instrumentation required to monitor, control, and operate a processing plant, unit operation, boiler, machine, or any other system that requires measurement, indication, control, modulation, and/or switching of variables.
Primary instrumentation, hardware and software devices, and functions that measure, monitor, control, and calculate, and application software functions that require or allow userassigned identities, shall be assigned both loop and functional identification.
Secondary instrumentation, such as hardware devices that measure and monitor, as well as level glasses, pressure gauges, and thermometers, shall be assigned only a functional identification.
Loop and functional identification shall be assigned in accordance with the guidelines in the standard or with modified guidelines based on the standard, established by the user or owner of the plant, unit, or facility in which the instrumentation is to be installed.
A unique loop identification number shall be assigned to identify each monitoring and control loop. A unique instrument identification/tag number based on the loop identification number shall be assigned for each monitoring or control loop to identify each of the following:
a) Hardware device and integral functions
b) Application software functions that require or allow a
user-assigned unique microprocessor or computer address
A monitor or control loop consists of some or all of the following (as indicated):
a) Measurement of the process variable (monitor and control):
1) Measuring element device, such as an orifice plate or thermocouple
2) Measurement transmitter, with an integral measuring element, such as a pressure transmitter or without an integral measuring element, such as a temperature transmitter and thermocouple
b) Conditioning of the measurement or input signal (monitor and control):
1) Calculating devices
2) Calculating functions
3) Safety barriers
c) Monitoring of the process variable (monitor):
1) Indicating or recording device
2) Application software display function
d) Controlling of the process variable (control):
1) Indicating or recording control device
2) Application software control function
e) Conditioning of the controller or output signal (control):
1) Calculating devices
2) Calculating functions
f) Modulation of the manipulated variable (control):
1) Control valve modulation or on–off action
2) Manipulation of another control loop setpoint
3) Limiting another control loop output signal
Secondary instrumentation shall be assigned instrument identification/tag numbers or other forms of identification in accordance with the guidelines established in the ISA standard or with modified guidelines based on the standard established by the user/owner of the plant, unit, or facility in which the instrumentation is to be installed.
Examples of instrument identification systems will be found in a future series of S5.1 (now ANSI/ISA-5.01.01) Technical Reports.
Instrument Index
Loop identification numbers and instrument identification/tag numbers shall be recorded in an instrument index (either manually generated or computerized instrument database), which shall be maintained for the life of the facility for the
recording and control of all documents and records pertaining to the loops and their instrumentation and functions.
An instrument index shall contain references to all instrumentation data required by owner or government regulatory agency management-of-change requirements. It should contain, as a minimum, for each loop:
a) Loop identification number
b) Service description
c) Instrument identification/tag numbers
d) Piping and instrument (P&ID) drawing numbers
e) Instrument data sheet numbers
f) Location plan numbers
g) Installation detail drawing numbers
Guideline Modifications
These guidelines may be modified to suit the requirements of the following:
a) Existing user-designed identification and numbering schemes that are not included in this standard
b) Computer databases used for record keeping
c) Microprocessor-based monitoring or control systems When modified guidelines are adopted, they shall be fully described and detailed in the user/owner’s engineering or
design standards.
Multipoint, Multivariable, and Multifunction Devices
Input and output devices and functions that are components of a multipoint device shall have tag suffixes that delineate between the different components.
Multivariable devices that receive two or more input signals, transmit one output signal, and have been assigned measured/initiating variable multivariable [U], shall have the following indicators:
a) Each different input shall be assigned its own loop identification number, and each output indicating, recording, switching, alarming, or other device and function that is actuated solely by a single variable, shall be assigned an instrument/tag number that identifies it as part of these loops.
b) Each indicating, recording, switching, alarming, or other device or function that is actuated by more than one of the multivariables shall be assigned an instrument/tag number that identifies it as part of the multivariable loop.
Multifunction devices that receive two or more input signals, send out two or more output signals, or perform two or more functions may be assigned readout/passive or output/active function multifunction [U] and shall have a loop number assigned according to the measured/initiating variable.
Loops that perform two or more functions from a single measured/initiating variable may have the following:
a) Each function assigned a unique instrument/tag number and shown on diagrams as multiple tangent bubbles for the integral functions and multiple individual bubbles for the nonintegral functions.
b) One readout/passive and/or output/active function designated by succeeding letter [U], for the integral functions and multiple individual bubbles for the nonintegral functions, and, if necessary, a note or comment defining the integral functions.
Graphic symbol examples of these loops are given later in this section.
System Identification
Instrumentation is often assembled into systems for various reasons including ease of purchase, ease of application, compatibility, and so on. These systems may need to be identified on drawings and in text.
Some of the more common instrumentation systems and the system codes for identifying them are the following:
ACS = Analyzer control system
BMS = Burner management system
CCS = Computer control system
CEMS = Continuous emissions monitoring system
DCS = Distributed control system
FDS = Flame detection system
MMS = Machine monitoring system
PCCS = Personal computer control system
PLC = Programmable logic controller
SIS = Safety instrumented system
VMS = Vibration monitoring system
Suffixes may be added to the instrumentation system codes [SC] when required as follows:
a) [SC] 1, [SC] 2, and so forth, when more than one system is used in a complex
b) [SC]-M, [SC]-L, when main and local systems are used in a unit
c) [SC]-[unit identifier]
Loop Identification Number
A loop identification number is a unique combination of letters and numbers that is assigned to each monitoring and control loop in a facility to identify the process or machine variable that is being measured for monitoring or control (see Table 1.1a).
Loop identification numbers are assigned as follows:
a) Numerals in parallel, serial, or parallel/serial sequences
b) Letters or letter combinations selected from Table 1.1c, Identification Letters (column 1, Measured/Initiating Variables and column 2, Variable Modifiers)
Loop identification number numerals shall be assigned to loop variables letters according to one of the following sequencing methods:
a) Parallel: duplicated numerical sequences for each loop variable letter or letter combination
b) Serial: the same numerical sequence regardless of loop variable letter or letter combination
c) Parallel/serial: parallel sequences for selected loop variable letters or letter combinations and a serial sequence for the remainder Loop number numerical sequences are normally three or more digits, -*01, -*001, -*0001, and so on, where
a) -* can be any digit from 0 to 9
b) Coded digits are related to drawing numbers or equipment numbers
c) *00, *000, *0000, and so on are not used
Gaps may be left in any sequence to allow for the addition of future loops. (See Tables 1.1c through 1.1f for various
combinations of allowable instrumentation identification/tag numbers.)
IDENTIFICATION LETTER TABLES
See statement of permission.
General
This clause provides in tabular form the alphabetic building blocks of the Instrument and Function Identification System in a concise, easily referenced manner.
Table 1.1c, Identification Letters, defines and explains the individual letter designators to be used as loop and functional identifiers in accordance with the guidelines of the subsection titled “Identification System Guidelines.”
The letters in Table 1.1c shall have the mandatory meanings as given in the table except as follows:
a) The user shall assign a variable name to the user’s choice letters in column 1 and a function name to the user’s choice letters in columns 3 through 5 when such letters are used.
b) The user may assign meanings to the blanks in columns 2 through 5 if needed.
Table 1.1d, Allowable Loop Identification Letter Schemes, provides the allowable loop identification letters and combinations according to the loop identification number construction schemes.
The letters and combinations shall have the mandatory meanings as given in the table except as follows:
a) The user shall assign a variable name to the user’s choice letters in the “First Letter” column.
Tables 1.1e and 1.1f, Allowable Function Identification Letter Combinations, provide allowable combinations of function identifying letters.
The letter combinations shall have the meanings given in the table, except as follows:
a) The user shall assign a variable and/or function to user’s choice letters if used.
b) The user may assign a meaning to blanks if needed.
c) Cells marked N/A are combinations that shall not be allowed.
See statement of permission.
N/A = not allowed.
Note (1): Alarm combinations are given with Function Modifiers for deviation from set point and absolute values. Adding [H] or [L] forms low–low and high–high alarm Functional Identifications.
Note (2): Readout/Passive Function [G] (glass, gauge) is shown for local direct connected devices, such as flow sight glasses, level glasses, pressure gauges, and thermometers, and also for weigh scales and position indicators. These devices provide a simple view of a process condition. The Readout/Passive Function [I] (indicate) may continue to be used in facilities where it is currently used.
See statement of permission.
N/A = not allowed.
Note (3): The combinations in the [IC] and [RC] columns indicate the order to be followed in forming the Functional Identification of a controller device or function that also provides indication or recording.
Note (4): The combinations in the [C] column do not have operator visible indication of measured variable, set point, or output signal, when used with discrete hardware single case instruments.
Note (5): The combinations in the [C] column may also be used for a controller function configured in a shared or distributed control system.
Note (6): The combinations in the [CV] column indicate the order to be followed in forming the Functional Identification for self-actuated control valves.